PHOENIX (AP) -- Growing concerns about allegations of gross mismanagement and neglect at the Phoenix VA Health Care Center have resulted in a commitment by the chairman of the Senate Veterans' Affairs Committee to hold a hearing, members of Arizona's congressional delegation said Thursday.

Republican Sens. John McCain and Jeff Flake raised concerns last week and again Wednesday. Democratic Reps. Raul Grijalva, Kyrsten Sinema and Ann Kirkpatrick also joined the effort, calling for an independent investigation.

Sen. Bernard Sanders of Vermont, chairman of the committee, said the hearing will follow an investigation by the VA Office of Inspector General. A team of investigators is in Phoenix and an objective inquiry is needed before any kind of informed deliberation can happen, Sanders said.

"Congress must fulfill its responsibilities to get to the truth without delay," McCain and Flake said in a statement. "Our nation has a duty to provide the best quality of care to those who have served and sacrificed on our behalf, and we must hold accountable anyone who would break that solemn obligation."

The lawmakers described the allegations of delays in care, gross mismanagement, neglect and false record-keeping at the medical center as "deeply disturbing."

Kirkpatrick and Sinema were in Tucson on Thursday to participate in a House Committee on Veterans Affairs field hearing focused on mental health care and traumatic brain-injury treatment for veterans. Too many returning veterans are not getting the support and care they need, Sinema said.

"To learn of additional allegations that veterans who have served our country have been and are still denied lifesaving treatments is simply unacceptable," Sinema said.

Iraq War veteran Derek Duplisea of Tucson testified during the field hearing that veterans are often at the end of their rope when they finally seek help from VA medical centers. They often experience "deep frustration and even despair if they are told to wait six weeks or longer to begin therapy," he said.

Recently, the chairman of the House committee said the panel's investigators concluded as many as 40 veteran deaths in Arizona could be related to delays in care.

Phoenix VA Health Care System officials said they have asked for an external review by the Inspector General and will address any problems quickly.

The congressional discussions about delayed health care for veterans come amid an investigation of whistleblower claims by The Arizona Republic. Sam Foote, a retired physician from the Phoenix VA, provided the newspaper with documents he filed with the VA Office of Inspector General seeking investigations of alleged medical-care failures and administrative misconduct.

Foote and other whistleblowers accused Arizona VA executives of collecting bonuses for reducing patient wait times, yet they charged that the purported successes resulted from data manipulation rather than improved service for veterans.